This invention relates to a vehicle for transporting loads of substantial weight and, more particularly, to an improved article storage and retrieval storage rack entry vehicle for use in warehousing systems.
A variety of systems have been employed in the past for the storage and retrieval of articles in high volume warehouses. One such system comprises a plurality of storage racks having a plurality of storage bins and in which the racks are separated from each other by aisles. In such system a vehicle having an elevatable platform is movable in the aisles. Forks or the like are carried on the elevatable platform which are extendable from either side of the platform into selected ones of the bins in the storage racks such that an article may either be stored in or retrieved from a particular bin when the elevatable platform is positioned in front of the desired bin. An example of such system is shown in U.S. Pat. No. 3,805,973. The disadvantage of such system is that the density of storage for a storage space of given cubic volume is reduced because of the large number of aisles that must be provided for operation of the storage and retrieval vehicle.
In order to minimize this loss of storage density, various high density storage systems have been devised in which the number of aisles per cubic volume of storage space have been substantially reduced and replaced by storage structure. One such high density system employs storage racks having elongate inclined bins with idler rollers in the bottom of the bins. These bins open at one end and at a slightly higher elevation, to the face of the storage racks where articles are inserted into the bins so as to roll down the inclined idler rollers toward the other, lower retrieval end of the bin. The stored articles are removed, on a first in-first out basis, from the opposite lower elevation end of the rack bins. Another form of high density storage system comprises elongate bins extending from one face to the other of the storage racks, but these bins are substantially horizontal, rather than inclined. In such horizontal bin systems, a rack entry vehicle is employed which moves into the elongate bins in the rack to either store an article in the bins at a designated location or retrieve a designated article from the bin. It is this latter form of high density storage system with which the present invention is concerned.
Rack entry vehicles in such high density systems are subject to several potential problems. For example, the loads which such vehicles must handle are frequently of substantial weight, sometimes as much as 2-3 tons. Moreover, even though the loads handled by the rack entry vehicles are frequently palletized, the loads may still be unevenly distributed. Compounding this problem is the fact that the storage racks in such systems are frequently many stories in height and are of substantial length and width. Accordingly, the racks and the surfaces upon which the rack entry vehicle must operate are subject to distortion not only from contraction and expansion due to temperature variations, but also due to structural settling. The combined result of such unequal weight distribution and distortion frequently results in at least some degree of elevational variation of the rails upon which the race entry vehicle must run. This, in turn, presents a condition wherein one or more of the wheels of the rack entry vehicle may leave their support surface resulting in a loss of traction of the wheels which have left the surface, possible collision of the load with the rack structure during movement of the vehicle in the bins and increased loading on the remaining wheels and their bearings.
Spring loading of the vehicle wheels has been considered to overcome this problem. However, such spring loading is inadequate for several reasons. Spring loading mechanisms are relatively complex and are, thus, subject to maintenance problems. Even more significantly, such spring loading mechanisms are space consuming due to their complexity. This is a significant disadvantage due to the fact that rack entry vehicles are limited in length and width to the dimensions of the pallets or loads which are to be handled, and in height by the distance between the bottom of the load or its pallet and the top of the load in the next lower bin. In fact, the latter distance is usually purposely designed to be a minimum to maximize storage density. Thus, the volume aboard such rack entry vehicles for carrying necessary operational components, such as drive motors for both the horizontal and platform lift drives, electrical circuitry, batteries and other control mechanisms, is at a premium. Accordingly, it is advantageous to reduce or eliminate, if possible, any mechanisms which consume space. Another disadvantage of such spring loading mechanisms is that they may be unstable in wide or poorly distributed load conditions.
In the present invention, the vehicle wheels are maintained in continuous contact with their rolling surfaces without the need for complex spring loading systems. In the present invention, several of the elements or components of the rack entry vehicle which might otherwise have been incorporated in the vehicle anyway, are utilized in a particular configuration to overcome the possibility of the wheels leaving the rails. Thus, space consumption, maintenance and capital expenditure for the components themselves are substantially reduced.
In a principal aspect of the present invention, a vehicle for transporting loads of substantial weight, comprises a plurality of transport means spaced from each other in the direction of both the length and width of the vehicle, the transport means supporting the vehicle for movement upon a surface. Support means are provided for supporting the load on the vehicle and to distribute the weight of the load to locations adjacent each of the transport means. Rigid plate means, connects both the plurality of transport means and the support means, the plate means is sufficiently flexible to flex due to weight of the vehicle and the loads thereon to maintain each of the transport means in continuous contact with the surface when a portion of the surface upon which a given one of the transport means varies in elevation from other portions of the surface upon which the other ones of the transport means rest.
The plate means can be a single sheet or a composite of more than one piece. The main feature is that the plate means provides a rigid, but sufficiently flexible, connection between the various support and transport means of the vehicle to maintain the vehicle wheels in continuous contact with their running surfaces even though these surfaces may vary in elevation.
In another principal aspect of the present invention, a plurality of storage racks for the storage of the loads is provided. The storage racks comprise a plurality of elongate bins for supporting a plurality of the loads therein. Rail means are positioned in each of the bins which extend for substantially the length of the bins and which define the surface upon which the vehicle moves. The aforementioned vehicle is movable over substantially the length of each of the bins for depositing and retrieving loads into and from the bins.
These and other objects, features and advantages of the present invention will be more clearly understood through a consideration of the following detailed description.